As modern merchandize transactions are extremely frequent, to prevent the merchandize from receiving external forces and becoming damaged, corrugated paper boxes and cushioning materials are extensively applied in product transportation. A corrugated paper box not only is light and rigid, but also internally includes a wavy sandwich core sheet that is flexible and shock absorbent. Thus, an object in the corrugated paper box can be better protected, and damages caused by external vibrations upon the object can also be reduced. For example, the Taiwan Patent 1271363 discloses an improved cardboard box structure. The improved cardboard box structure includes a surrounding side plate, and a plurality of covering wing plates disposed at two sides of the surrounding side plate. At least one of the covering wing plates includes a positioning lug. During an application process of the improved cardboard box, the surrounding side plate is surrounded to form an accommodating space, the covering wing plates are bent to cover two opposite sides of the accommodating space, and the positioning lug is bent and connected at the surrounding side plate, thereby forming a packaging structure for an object to be placed therein.
However, as the surrounding side plate and the covering wing plates are single layer structures, the improved cardboard box structure is liable to be dented caused by impacts during the application process. Further, the improved cardboard box structure, after forming a box through bending, is only secured by connecting the positioning lug at the surrounding side plate. As a result, during the application process of the improved cardboard box structure, disengagement or separation due to a small connecting area of the positioning lug is easily incurred, such that the improved cardboard box structure becomes incapable of maintaining the box structure for accommodating the object.